JPH08178863A - Method for inspecting defect of lenticular lens sheet - Google Patents

Abstract

PURPOSE: To improve the S/N of signal for detecting defect and to improve quality by obtaining an angle where the ratio of standard deviation of the differential signal of a defective part and that of a defect periphery part is maximized, and setting the angle formed by a lenticular lens sheet surface of a linear region image pick-up means to an angle where the ratio with the standard deviation may maximized. CONSTITUTION: The value of an angle θ formed for the surface of a lenticular lens sheet 30 of linear region image pick-up means 20A and 20B for picking up a specific linear region with reflection dark field light is swept when the position of a lighting means 10 is set to a specific angle formed for the lenticular lens sheet 30 for the positional relationship between a linear region image pick-up means 20 and the lighting means 10, a standard deviation N between a differential signal S at a defective part corresponding to various values of θand the differential value of a defect surrounding part is obtained, an angle θ2 where the S/N ratio between the differential signal S at the defective part and that of the defect surrounding part may be maximized is obtained, and an angle to the surface of the lenitcular lens sheet 30 of the linear region image pick-up means 20A and 20B is set to be θ2 for picking up an image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting the appearance of a lenticular lens sheet used for a transmission type projection screen, and more particularly to an automatic method for in-line detection of white defects in a black stripe portion of a lenticular lens sheet. The present invention relates to an inspection device method.

[0002]

2. Description of the Related Art A lenticular lens sheet for a transmissive projection screen is made of a transparent resin such as an acrylic resin or a polycarbonate resin. As shown in FIG. 6, generally, the light source side and the light emitting surface when used as a screen. Lenticular lenses 61 and 62 are provided on the side, and a light-shielding stripe portion called a black stripe 63 is provided between the lenticular lenses 61 on the light emitting surface side to increase the contrast and make the image sharp. The light-shielding stripe portion called the black stripe is formed by extruding the lenticular lens sheet 60 with an acrylic resin, a polycarbonate resin or the like, and then printing the light-shielding film portion while passing it between the rolls. , A part that is partially missing or damaged in the process of manufacturing the light-shielding film part or thereafter (hereinafter,
(Referred to as white defect) occurs. For this reason, when used as a screen, it is a cause of impairing contrast and sharpness of the image due to reflected light from the outside,
It was necessary to identify and correct the location or to selectively remove the screen, and it was necessary to identify the location of the white defect portion.

Conventionally, as a visual inspection method for detecting the above-mentioned white defects of a lenticular lens sheet, a method by human eyes has been adopted, but in recent years, a lenticular lens sheet for a transmission type projection screen has a high quality. With the increasing demand for higher quality and mass production, the conventional naked-eye inspection has differences in people and reproducibility. Therefore, inexpensive automatic inspection equipment has been demanded. Also, for mass production, inspection by an automated device has been required. In order to deal with this, the inventors of the present application have shown that the lenticular lens sheet 74 at least in a direction substantially perpendicular to the moving direction of the lenticular lens sheet 74 as shown in FIG.
, A CCD line sensor camera 71 which is a linear area imaging means for imaging with reflected dark field light, and a light source which is an illumination means for supplying reflected dark field illumination for imaging. 72 and an image processing hand portion 73 for detecting a defect based on image data obtained by the linear area image pickup means, and a continuous plate-shaped lenticular lens sheet 74 is attached in the direction of the lenticular lens (black stripes). (While moving at a constant speed)
A defect inspection method for detecting a defect of the lenticular lens sheet 74 has been proposed. In this method, the light from the lenticular lens sheet 74 is simply transferred to the CCD.
By the line sensor 71, substantially right above the lenticular lens sheet 74, that is, the lenticular lens sheet 74.
The image was taken by the reflective dark-field illumination so that the angle formed with the surface of the plane was about 90 degrees. However, with the increasing demand for higher quality and mass production, the above method allows black stripes of 300 μm or less to be white even if the field of view of the CCD line sensor camera is small (even if the magnification is increased). The defect could not be detected, which was a problem. The reason why the white defect of the black stripe of 300 μm or less cannot be detected is that the diffusing material mixed inside the lenticular lens sheet is
It was said that the S / N for defect detection would be lowered, but no suitable method for improving the S / N has been proposed.

[0004]

In this way, the lenticular lens is subjected to reflection dark-field illumination, and the image picked up by the linear region image pickup means is subjected to image processing to produce white defects on the black stripes of the sample on the production line (in-line). Even in the automatic inspection method that is detected by, the defect inspection method that can cope with higher quality and mass production has been required. Under the circumstances, the present invention provides an automatic inspection in which a lenticular lens is subjected to reflective dark-field illumination and image processing is performed on an image captured by a linear area imaging unit to detect a white defect in a black stripe portion of the lenticular lens. In the method, it is intended to provide an automatic inspection method capable of improving the S / N of a signal for detecting a defect and coping with further improvement in quality.

[0005]

A method for inspecting a defect of a lenticular lens sheet according to the present invention includes at least a width in a direction substantially perpendicular to a moving direction of a sheet-shaped or continuous plate-shaped lenticular lens sheet. One or a plurality of linear area imaging means for imaging a predetermined linear area of the lenticular lens sheet with reflected dark field light, and reflective dark field illumination for imaging the linear area imaging means. An illumination means for supplying and an image processing means for detecting a defect based on the image data obtained by the linear area image pickup means are provided, and the defect of the lenticular lens sheet is moved while moving the lenticular lens sheet at a constant speed. In the defect inspection method for detecting a lenticular lens sheet, the angle between the illuminating means and the lenticular lens sheet surface is set to a predetermined angle θ1. -When the image of the lens sheet is taken, the value of the angle θ formed with the lenticular lens sheet surface of the linear area imaging means for taking an image of the predetermined linear area with reflected dark field light is used to detect the defect portion corresponding to various θ values. Differential signal S1
And the standard deviation N1 of the differential signal around the defect and the differential signal S1 of the defective part and the standard deviation N1 of the differential signal around the defect.
The angle θ2 at which the ratio S1 / N1 with the maximum is obtained, and the angle formed with the surface of the lenticular lens sheet of the linear area image pickup means is set to θ2, and an image is taken.
The standard deviation N1 of the differential signal S1 of the defective portion and the differential signal of the peripheral portion of the defect is preferably the secondary differential signal when the actual defect detection is performed using the secondary differential signal. As shown in FIG. 3A, in the above description, the angle θ1 formed with the lenticular lens sheet surface of the illuminating means means a direction from the illuminating means to a predetermined linear area where the image is captured by the image capturing means, that is, a field of view area. The angle θ formed by the image pickup means and the lenticular lens sheet surface is an angle formed by the image pickup means and the lenticular lens sheet surface, and the angle θ formed by the image pickup means is a predetermined linear area taken by the image pickup means, that is, the direction to the image pickup visual field area and the lenticular lens sheet surface. It is an angle, and the illuminating means and the image pickup means are on opposite sides to each other with respect to the normal line in the photographing field area of the lenticular lens surface.

[0006]

According to the lenticular lens sheet defect inspection method of the present invention, the lenticular lens is subjected to reflection dark field illumination by the above-mentioned structure, and the image taken by the linear area image pickup means is subjected to image processing to obtain a sample. In the automatic inspection method for detecting the defects of (1), it is possible to provide an automatic inspection method capable of coping with higher and higher quality. Specifically, the positional relationship between the linear area imaging means and the illuminating means reflects the predetermined linear area when the angle formed by the position of the illuminating means with respect to the lenticular lens sheet surface is set to a predetermined angle θ1. The differential signal S of the defect portion and the differential signal of the peripheral portion of the defect corresponding to various values of θ are given by changing the value of the angle θ with respect to the surface of the lenticular lens sheet of the linear area image pickup means that takes an image with dark field light. The standard deviation N is obtained, and the ratio S / N of the differential signal S of the defective portion and the standard deviation N of the differential signal of the peripheral portion of the defect
Is obtained, the angle formed with the lenticular lens sheet surface of the linear area image pickup means is set to θ2, and an image is taken to detect defects due to the influence of the diffusion material mixed in the lenticular lens sheet. The decrease in S / N is minimized.

[0007]

EXAMPLES Examples of the defect inspection method for a lenticular lens sheet according to the present invention will be given below to explain the present invention with reference to the drawings. The defect inspection method for the lenticular lens sheet of the embodiment is a defect inspection method for detecting a defect (white defect) in the light-shielding film portion of the light-shielding stripe portion, which is called a black stripe 630 shown in FIG. The overall functional configuration of the apparatus for defect detection is shown in FIG. FIG. 2 is a diagram showing the relationship between the image pickup means (CCD line sensor) of the defect detection apparatus shown in FIG. 1, the image processing apparatus, and the like. In FIGS. 1 and 2, 10 is an illuminating means, 20A and 20B are CCD line sensor cameras, and 21.
A and 21B are CCD line sensor camera controllers,
30 is a lenticular lens sheet, 40, 40A, 4
Reference numeral 0B indicates an imaging field of view, and reference numeral 50 indicates an image processing device. As shown in FIG. 1, the apparatus for detecting a defect is provided with an image pickup means 20 including two CCD line sensor cameras 20A and 20B and an illuminating means 10 on an upper side of a passage surface of a lenticular lens sheet 30. In FIG. 1B, the two lines extending from the CCD line sensor cameras 20A and 20B respectively represent the visual field taken by the cameras. The image pickup means controller 21 shown in FIG. 2 is for adjusting the value of the angle θ formed by the image pickup means 20 with respect to the surface of the lenticular lens sheet 30.

The inspection method of this embodiment detects defects by using the defect detecting apparatus shown in FIGS. 1 and 2, and allows the lenticular lens sheet 30 to pass through at a constant speed. Two CCD line sensor cameras 2
The imaging field areas 40A and 40B of the lenticular lens sheet 30 are respectively imaged by 0A and 20B, and the entire imaging field of view 40 of a predetermined area of the lenticular lens sheet 30 is obtained at the same time. Is set to a predetermined angle θ1 with respect to the lenticular lens 30, the lenticular lens 3 of the CCD line sensor cameras 20A and 20B that images the imaging field 40 by using the light from the illumination means 10 as dark field illumination.
The angle θ with respect to 0 is optimized, and this makes it possible to cope with the high quality of the lenticular lens 30.

CCD line sensor cameras 20A, 20B
As shown in FIG. 2, the image signals (data) obtained by the above are respectively processed by the image processing unit 50, and in addition, the image signals of the entire imaging visual field 40 of the predetermined region of the lenticular lens sheet 30 are processed. It Image processing is CCD
The spatial filter is used for the image data (signal) obtained by the line sensor cameras 20A and 20B, and the primary differential processing or the secondary differential processing is performed.

Hereinafter, the inspection method of this embodiment is performed as described above, and a specific procedure will be described with reference to FIG.
First, as shown in FIG. 3A, the illuminating means 10 is formed by a direction in which the illuminating means irradiates the imaging visual field region 40 having a predetermined defect (white defect) of the lenticular lens sheet 30 with the lenticular lens sheet surface. Angle is a predetermined angle 30
Set to be °. Next, the CCD line sensor cameras 20A and 20B and the imaging field areas 40A,
While changing the value of the angle θ formed by the direction of the camera connecting 40B and the lenticular lens sheet 30 as shown in Table 1, the secondary differential signal S1 of the defective portion corresponding to various θ values and two values around the defective portion. The next differential signal standard deviation N1 is detected.
The differential processing is for enhancing the signal of the defective portion, but noise that cannot be removed is also detected. Then, FIG.
As shown in (b), the ratio S1 / N1 between the secondary differential signal S1 of the defective portion and the standard deviation N1 of the secondary differential signal around the defective portion corresponding to the obtained values of θ is obtained. The ratio S in FIG. 3 (b)
Graphing 1 / N1 results in Fig. 3 (c), where S
The value of θ showing the maximum value of 1 / N1 is about 50 °. Here, assuming that the secondary differential signal S1 of the defective portion is the signal S, the standard deviation N1 of the secondary differential signal around the defective portion is the noise signal N.
Of the defect detection S / N
In order to find the optimum angle, the angle θ2 that maximizes the ratio S1 / N1 in the dark-field reflection imaging is found, and this is calculated as S / N.
Can be set to an optimum angle. In this manner, the angle θ formed by the linear area imaging means with respect to the lenticular lens sheet surface of the linear area image pickup means, which corresponds to the predetermined angle of 30 ° with respect to the lenticular lens sheet surface of the illumination means 10, is Decide to be about 50 °.

The reason why the angle θ formed by the linear area image pickup means with respect to the surface of the lenticular lens sheet suitable for defect detection is determined in this way is as follows. A diffusing material is dispersed inside the resin of the lenticular lens sheet, and the diffusing material is oriented in a random direction. Due to the influence of the diffusing material, the CCD line sensor cameras 20A and 20B have the same lenticular lens sheet as the defective portion. Three
A signal that locally changes depending on the location of 0 is detected. For this reason, it cannot be removed by differential processing similar to the differential processing in the defect inspection described later, and as a result, it remains as a noise signal in addition to the defect signal. This is the first reason. Then, in the resin of the lenticular lens sheet, the diffusing material is oriented in a random direction inside the resin, but as shown in FIG. 3B, due to the angle of light incident on the lenticular lens sheet,
The second reason is that the noise signal (light intensity) changes differently from the defect signal depending on the direction of the light emitted from the diffusing material.

These processes are performed by the image processing device 5 shown in FIG.
0, and in this way, the lighting means 1
0, CCD line sensor camera 20 as image pickup means
Although the actual defect detection is performed after the directions (angle θ) of A and 20B are determined, it is device-wise that the image processing unit for this defect detection also serves as the image processing when determining the angle θ. The same applies to the image processing apparatus 50 that is simple and is used in the defect inspection method for the lenticular lens sheet of this embodiment. At the time of actual defect detection, the image signal (data) obtained by the CCD line sensor cameras 20A and 20B is subjected to a first-order differential processing or a second-order differential processing in the image processing unit 50 by using a spatial filter for the image data (signal). Differentiating processing is performed, and the obtained results are further subjected to slicing processing to detect defects exceeding a predetermined threshold as defects.

The material of the lenticular lens sheet used in this embodiment is acrylic (refractive index 1.51).
The diffusing material is a glass having a refractive index of 1.53 to 1.54, an average size (particle diameter) of 17 μm (MAX 38 μm), and 4% by weight of acrylic. The defect detecting method of the present embodiment determines the optimum angular position for image pickup by the linear area image pickup means (CCD line sensor camera) by the above-mentioned procedure. Basically, a wrench as shown in FIG. In the case of the cue lens sheet, the white defect detection S /
It is possible to improve N.

Then, the illuminating means 1 is operated as described above.
0, a process for detecting a defect in the image processing unit 50 shown in FIG. 2 in the image data obtained by the image pickup of the apparatus in which the position of the image pickup means is set will be briefly described. The image processing unit 50 shown in FIG. 2 obtains the change of the signal by specifying the defect by performing the first-order differential processing or the second-order differential processing of the image signal obtained by the image pickup. Is a product-sum operation for each sampling using a filter having an element array. Here, using obtained from the imaging means, the image data P (X _ij) a spatial filter table W a (i, j), P ( X ij)
And the W (i, j) sum-of-products operation is called a filtering process, and the table W (i,
j) is called a filter, and is generally called a differential filter or a space filter. The differential filter for the array of pixel data in the Y direction is shown in FIG. 4 according to the weight of the pixel of interest and the pixels before and after it in the product-sum operation and the array direction.
It is expressed as. For example, for the image data P (Y _n ), by setting (+1, −2, +1) and the spatial filter table (weight table) as shown in FIG. 4A, smoothing processing for two pixels in the Y direction is performed. The second derivative processing can be performed. If the pixel of interest is Y _n , the image data P
Sum of products operation S of (Y _n ) and the spatial filter table
_n is (+1) × Y _n−1 + (− 2) × Y _n + (+ 1) ×
Y _{n + 1} . Further, as shown in FIG. 4B, (-1, +
By setting the spatial filter table (weight table) in 1), the primary differential processing can be performed.

The image processing unit 50 controls the CC of the photographing device 110.
For each image data (signal) of the D line sensor cameras 20A and 20B, for example, the following processing is performed to detect a defect. FIG. 5 is a diagram for explaining image processing on image data (signal) obtained from one CCD line sensor camera. In the second derivative in FIG. 5, line data obtained by sampling by the CCD line sensor camera is subjected to product-sum calculation with the spatial filter table for each pixel data at the same position between lines, and the predetermined value is predetermined. The line data obtained by the continuous sampling of a number is accumulated, and the product-sum operation is performed between the line data. In the case of FIG. 5, this process is performed between 9 line data, but every time new line data is sampled, the old line data is removed gradually, and this process is always performed with 9 line data. ) _Represents the pixel data at the i-th position in the j-th line data, and when the pixel data at the M-th position is subjected to the multiply-accumulate operation between the lines, the results of the secondary differential processing and the primary differential processing are respectively As shown in FIGS. 5B and 5C. For each operation result of the second order differential processing or each operation result of the first order differential processing obtained in this way,
Further, slicing is performed to detect defects that exceed a predetermined threshold value. Here, the line data is
The above-mentioned predetermined one of the imaged data in one sampling of the visual field obtained by the image pickup means (CCD line sensor camera) and spanning the width in the direction substantially orthogonal to the moving direction of the lenticular lens sheet and including the predetermined width on a straight line on the sheet surface It says data corresponding to the entire width.

[0016]

As described above, the present invention provides an automatic inspection apparatus for illuminating a lenticular lens sheet with reflection dark-field illumination and performing image processing on an image captured by the linear region imaging means to detect a defect in a sample. It is possible to provide a method for detecting white defects in a black stripe of a lenticular lens sheet that can be used for higher quality and mass production. Further, the present invention makes it possible to improve the S / N of a defect signal in the defect inspection of various lenticular lens sheets having different shapes and materials.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for performing a defect detection method for a lenticular lens sheet according to an embodiment.

FIG. 2 is an apparatus diagram for carrying out the lenticular lens sheet defect detection method of the embodiment.

FIG. 3 is a diagram for explaining a defect detection method for a lenticular lens sheet according to an embodiment.

FIG. 4 is a diagram showing a space filter.

FIG. 5 is a diagram for explaining image processing in the embodiment.

FIG. 6 is a diagram showing defects in a lenticular lens sheet.

FIG. 7 is a schematic view of an apparatus for explaining a conventional defect inspection method.

[Explanation of symbols]

10 Illuminating means (light source) 20 Imaging means 20A, 20B CCD line sensor camera 21A, 21B CCD line sensor camera controller 30 Lenticular lens sheet 40, 40A, 40B Imaging field of view 50 Image processing unit 60 Lenticular lens sheet 61, 61 Lenticular lens unit 63 Black stripe 71 CCD line sensor camera 72 Light source 73 Image processing unit 74 Lenticular lens sheet 75 Imaging field of view

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // G03B 21/62

Claims (1)

[Claims] 1. A predetermined linear region of at least a sheet-shaped or continuous plate-shaped lenticular lens sheet that extends across a width in a direction substantially perpendicular to the moving direction of the lenticular lens sheet by reflected dark-field light. One or a plurality of linear area imaging means for imaging, an illuminating means for supplying the linear area imaging means with reflected dark field illumination for imaging, and an image obtained by the linear area imaging means An image processing means for detecting a defect based on data, and a defect inspection method for detecting a defect of the lenticular lens sheet while moving the lenticular lens sheet at a constant speed, wherein the illuminating means includes a lenticular lens sheet surface. When the lenticular lens sheet is imaged by setting the angle formed by and to a predetermined angle θ1, the predetermined linear region is reflected by dark field light. The value of the angle θ formed with the lenticular lens sheet surface of the linear area imaging means to be imaged is changed, and the differential signal S1 of the defect portion and the standard deviation N1 of the differential signal of the peripheral portion of the defect corresponding to various θ values are obtained, and the defect portion is obtained. Ratio S1 / N1 of the differential signal S1 of the differential signal and the standard deviation N1 of the differential signal of the peripheral portion of the defect
A method of inspecting a defect of a lenticular lens sheet, which comprises: obtaining an angle θ2 at which the angle becomes maximum, setting an angle formed with the surface of the lenticular lens sheet of the linear region image pickup means to θ2, and performing image pickup.